Hearing aids can provide adjustable operational modes or characteristics that improve the performance of the hearing aid for a specific person or in a specific environment. Some of the operational characteristics are volume control, tone control, and selective signal input. One way to control these characteristics is by a manually engagable switch on the hearing aid. The hearing aid may include both a non-directional microphone and a directional microphone in a single hearing aid. Thus, when a person is talking to someone in a crowded room the hearing aid can be switched to the directional microphone in an attempt to directionally focus the reception of the hearing aid and prevent amplification of unwanted sounds from the surrounding environment. However, a conventional switch on the hearing aid is a switch that must be operated by hand. It can be a drawback to require manual or mechanical operation of a switch to change the input or operational characteristics of a hearing aid. Moreover, manually engaging a switch in a hearing aid that is mounted within the ear canal is difficult, and may be impossible, for people with impaired finger dexterity.
In some known hearing aids, magnetically activated switches are controlled through the use of magnetic actuators. For examples, see U.S. Pat. Nos. 5,553,152 and 5,659,621. The magnetic actuator is held adjacent the hearing aid and the magnetic switch changes the volume. However, such a hearing aid requires that a person have the magnetic actuator available when it desired to change the volume. Consequently, a person must carry an additional piece of equipment to control his\her hearing aid. Moreover, there are instances where a person may not have the magnetic actuator immediately present, for example, when in the yard or around the house.
Once the actuator is located and placed adjacent the hearing aid, this type of circuitry for changing the volume must cycle through the volume to arrive at the desired setting. Such an action takes time and adequate time may not be available to cycle through the settings to arrive at the required setting, for example, there may be insufficient time to arrive at the required volume when answering a telephone.
Some hearing aids have an input which receives the electromagnetic voice signal directly from the voice coil of a telephone instead of receiving the acoustic signal emanating from the telephone speaker. Accordingly, signal conversion steps, namely, from electromagnetic to acoustic and acoustic back to electromagnetic, are removed and a higher quality voice signal reproduction may be transmitted to the person wearing the hearing aid. It may be desirable to quickly switch the hearing aid from a microphone (acoustic) input to a coil (electromagnetic field) input when answering and talking on a telephone. However, quickly manually switching the input of the hearing aid from a microphone to a voice coil, by a manual mechanical switch or by a magnetic actuator, may be difficult for some hearing aid wearers.
There is a need in the art for a system which detects a time varying magnetic field and which receives information from the time varying magnetic field. The system should be compact and not require undue amounts of power.